Conventionally, modacrylic fibers have a hand like animal fur and, owing to such characteristics, have been used for standing hair products such as toys and clothing. In particular, for the purpose of providing the feeling of standing hairs and a natural external appearance, a down hair portion is formed of shrinkable fibers and a guard hair portion is formed of non-shrinkable fibers for external appearance in many cases.
Pile fabrics need to have a good external appearance, so that the shrinkable fibers also have to have various hues. However, since the shrinkable fibers shrink due to heat history incurred during a dyeing process, there currently are only the fibers whose hues are limited to those colored in a spinning process.
So far, highly-shrinkable acrylonitrile-based synthetic fibers have been obtained from a copolymer formed of 30 wt % to 58 wt % of acrylonitrile, 70 wt % to 42 wt % of vinylidene chloride and vinyl chloride and 0 wt % to 10 wt % of at least one kind of ethylenic unsaturated monomer (see Patent document 1). However, according to the knowledge of the inventors of the present invention, the above-noted shrinkable fibers shrink in dyeing at 70° C. or higher and no longer shrink greatly by the heat in a tentering process, in which an adhesive is applied to a back surface of a pile and dried, during pile processing. Further, although it is possible to suppress the shrinkage by dyeing at a temperature lower than 70° C. and allow the fibers to shrink by the heat in the tentering process, sufficient dye-affinity cannot be achieved. Patent document 1: JP 60(1985)-110911 A